Typically, the disposition of the intake or exhaust port in the cylinder head largely affects the engine output. Therefore, the engine efficiency can vary more than or equal to 10% based on the disposition of the intake or exhaust port. Accordingly, it is important that the intake or exhaust port is accurately formed at a designated place in the cylinder head.
For measuring the disposition of the intake or exhaust port of the cylinder head, the cylinder head is typically cut off, then the size of each portion of the intake or exhaust port is measured. The cylinder head is conventionally cut off by using a wire cutting or sawing machine. Next, the exposed intake or exhaust port is measured by using a three-dimensional instrument or scanning device. However, there is a drawback in that cutting the cylinder head complicates the working procedure and the cut-off cylinder head cannot be re-used.